Blends of natural rubber (NR) and crosslinked poly(butadiene) (BR) are an important class of polymers widely used in automotive/tire industry due to their specific mechanical performance. The aim of this project is to selectively study the crosslinking phenomenon for each component of these blends (NR & BR) and its influence on the mechanical behaviour. Particularly the goal of this project is to determine, for the first time, the influence of the crosslinking density of each phase of the blend on the mechanical response during uniaxial stretching of the material. To achieve this goal, the structural evolution of the materials will be followed by means of simultaneous SAXS-WAXS experiments upon uniaxial stretching in order to determine the influence of the crosslinking density of each phase on the resulting mechanical behaviour. Also, the influence of the BR phase, which remain amorphous when the blend is deformed, on the crystallization of NR under stress will be studied in detail.